1. Field of the Invention
The invention relates to a tool for the chipless production or finishing of a thread on a workpiece, in particular a cold-forming tap or a thread-forming tap.
2. Background
In these tools, the thread is produced without chip removal by means of forming of the workpiece, in that so-called pressing lands, also referred to as forming wedges or teeth, effect a cold forming of the workpiece by the use of pressure. The advantage of these tools is that, as a result of the deformation of the surface and the associated compaction, the hardness of the material increases in the region of the thread profile and thus a more wear-resistant thread than in chip-forming thread production is obtained.
Known cold-forming taps, in particular for internal thread production, comprise a shank and a working region. The shank is generally of cylindrical construction and is accommodated and held, by its end facing away from the workpiece, in the chuck of a thread-producing device. The working region, in particular the forming region, is located on that side of the cold-forming tap which lies opposite the shank.
The forming region is provided with a shaping curve which runs spirally around the periphery and along which the pressing lands are configured as elevations.
In known cold-forming taps, the separation angle between two pressing lands following one upon the other along the shaping curve is equally large for all pressing lands. An imaginary rectilinear connecting lines between the tips of the pressing lands along the shaping curve form in a projection onto a surface perpendicular to the tool axis, except for radial deviations, substantially a regular n-sided polygon, wherein n pressing lands per revolution of the shaping curve about the tool axis are provided. Every nth. pressing land is arranged along a straight line parallel to the tool axis, which pressing lands arranged along a straight line form a so-called pressing web.